1. Field
The embodiment relates to a light emitting device, a method of manufacturing a light emitting device, a light emitting device package, and a lighting system.
2. Background
A light emitting device (LED) includes a p-n junction diode having a characteristic of converting electric energy into light energy. The p-n junction diode can be formed by combining group III-V elements of the periodic table. The light emitting device can represent various colors by adjusting the compositional ratio of compound semiconductors.
When a forward voltage is applied to an LED, electrons of an n layer are combined with holes of a p layer, so that energy corresponding to an energy gap between a conduction band and a valence band may be released. This energy is mainly realized as heat or light, and the LED emits the energy as light.
For instance, a nitride semiconductor represents superior thermal stability and wide band gap energy so that the nitride semiconductor has been spotlighted in the field of optical devices and high-power electronic devices. In particular, blue, green, and UV light emitting devices employing the nitride semiconductor have already been developed and extensively used.
Recently, as the demand for the high-efficiency LED has been increased, improvement of the intensity of light has been sought after. In order to improve the intensity of light, various attempts, such as improvement of a multi-quantum well (MQW) of an active layer, improvement of an electron blocking layer and improvement of a layer below the active layer, have been performed, but the great effect is not achieved.